Biomimetic Software Engineering Techniques for Dependability

Doctoral thesis, 2002

The powerful information processing capabilities of computers have made them an indispensable part of our modern societies. As we become more reliant on computers and want them to handle more critical and difficult tasks it becomes important that we can depend on the software that controls them. Methods that help ensure software dependability is thus of utmost importance. While we struggle to keep our software dependable despite its increasing complexity, even the smallest biological system in nature shows features of dependability. This thesis applies ideas from and algorithms modeled after biological systems in the research for and development of dependable software. Based on a theory of software development focusing on the internal models of the developer and how to support their refinement we present a design for an interactive software development workbench where a biomimetic system searches for test sequences. A prototype of the workbench has been implemented and evaluated in a case study. It showed that the system successfully finds tests that show faults in both the software and its specification. Like biological systems in nature exploits a niche in the environment the biomimetic search system exploits the behavior of the software being developed. In another study we applied genetic programming to evolve programs for an embedded control system. Although the procedure did not show much potential for use in real fault-tolerant software, the program variants could be used to visualize the difficulty of the problem domain, explore the effects of design decisions and trade off requirements. Taken together the works in this thesis support the claim that biomimetic algorithms can be used to explore requirements, design and test spaces in early software engineering phases and thus help in building dependable software.